Grain de-hulling apparatus

ABSTRACT

A grain de-hulling apparatus consisting of an elongated, curved passageway through which grain is propelled by a current of air, the concave internal surface of said passageway being provided with a coating of abrasive material against which said grain is urged by centrifugal force during its travel through said passageway, whereby hulls are removed from the kernels of grain by abrasive action, with a minimum of breakage or fracturing of the kernels.

United States Patent Stamatiou Mar. 14, 1972 [54] GRAIN DE-HULLING APPARATUS Dimitri S. Stamatiou, 6708 N. Wyandotte, Kansas City, Mo. 64118 [22] Filed: Dec. 8, 1969 [21] Appl.N0.: 882,934

[72] Inventor:

[52] 11.8. C1 [51] Int. Cl ..B02b 3/00 [58] Field ofSearch................. 146/32, 49 A, 49 B, 253, 254,

[56] References Cited UNITED STATES PATENTS 1,442,275 1/1923 Johnson 146/253 2,433,178 12/1947 Ware ..l46/253X "nun FOREIGN PATENTS OR APPLICATIONS 8,605 1890 Great Britain ..146/253 Primary ExaminerWillie G. Abercrombie Attorney-John A. Hamilton [57] ABSTRACT A grain de-hulling apparatus consisting of an elongated, curved passageway through which grain is propelled by a current of air, the concave internal surface of said passageway being provided with a coating of abrasive material against which said grain is urged by centrifugal force during its travel through said passageway, whereby hulls are removed from the kernels of grain by abrasive action, with a minimum of breakage or fracturing of the kernels.

3 Claims, 4 Drawing Figures GRAIN llJlE-IIIULLING APPARATUS This invention relates to new and useful improvements in grain de-hulling apparatus, and has as its principal object the provision of an apparatus which will remove the hulls from kernels of grain substantially without grinding, breaking, or fracturing of the kernels themselves. Presently, grain is most commonly de-hullecl either by subjecting it to a brushing action, or by partially grinding the entire kernels, including the hulls, separating the portions of the hulls thus freed from the remainder of the grain by air-classification methods, then repeating the process, grinding the grain finer each time until substantially all of the hull material has been removed. This process requires substantial time and comparatively elaborate equipment, and is therefore expensive, and is also not notably efficient insofar as the removal of the hulls is concerned. For these reasons, it would be highly desirable if the bulls could be completely removed in a single step, without any appreciable grinding, fracture or breakage of the remaining portions of the kernels. Once the hulls have been fully removed, the kernels may then be ground to flour in a single grinding operation or at least in far fewer steps than have heretofore been required. An apparatus capable of de-hulling grain substantially without breakage, fracture, or grinding of the remaining portions of kernels is the primary object of this invention. Generally, this object is accomplished by the provision of an elongated, curved passageway the internal concave surface of which is provided with an abrasive coating, and moving grain through said passageway by means of a current of air. The grain thus is held against the abrasive surface by centrifugal force as it moves through the passageway, and the hulls are cut or abraded away by said surface. The grain tends to slide or roll along the abrasive surface smoothly with very little bouncing or bounding so that there is little likelihood that the kernels will be broken or fractured by impact, either against said surface or against each other.

Another object is the provision of a de-hulling apparatus of the character described in which the pressure of the grain against the abrasive surface maybe selected according to the individual requirements of the particular grain being processed. For example, some grains have relatively spherical kernels that can move along the abrasive surface with greater pressures and higher speed with little tendency to bound or bounce therein and be broken by impact, while other grains have relatively elongated, non-spherical kernels which have a greater tendency to bounce and break, and therefore require less pressure or lower speed. Some grain kernels, while initially somewhat non-spherical, become sufficiently spherical after only a portion of the de-hulling has been completed that they can withstand greater pressures against the abrasive without fracturing. Some grain kernels are relatively hard and tough, while others are more easily broken. These variations can be accommodated in the present apparatus by proper selection of the degree of curvature and attitude of the passageway.

Other objects are simplicity and economy of construction, and efficiency and dependability of operation.

With these objects in view as well as other objects which will appear in the course of the specification, reference will be had to the accompanying drawing, wherein:

FIG. l is a partially schematic view of a grain dehulling apparatus embodying the present invention, including a horizontal sectional view of the de-hulling housing taken on line I-I of FIG. 2,

FIG. 2 is a fragmentary sectional view taken on line lIlI of FIG. 1,

FIG. 3 is a view similar to FIG. 2, but showing a modification of structure, and

FIG. 4 is a view similar to FIG. 2, showing a second modification of structure.

Like reference numerals apply to similar parts throughout the several views, and referring first to FIGS. I and 2, the numeral 2 applies generally to a housing which is generally flat and annular in form, and defines therein a spiral passageway 4. Said housing is disposed in a horizontal plane, and passageway 4 is provided with a tangential inlet 6 at its outer end, while the inner end portion thereof is curved more sharply inwardly, as indicated at h to discharge tangentially into a vertical tube 10 extending axially through the housing, the opening of passageway 4 into tube 110 being indicated at 112. With passageway 4 in flat spiral form, as in FIGS. l and 2, housing 2 may conveniently consist of a generally annular base plate 14 (see FIG. 2) with an integral spiral wall 116 rising therefrom to define passageway 4 between the convolutions thereof, with an annular cover plate 18 closing the top of said passageway. A gasket 20 is interposed between the cover plate and the upper edge of spiral wall 16, and the cover plate is held in place by bolts 22 around its edges (see FIG. 2). Thus passageway 4, as shown, is rectangular in cross-sectional contour. Actually, this cross-sectional contour is immaterial, except that the outer or concave wall of the passageway should be flat, that is, the generating line of this surface should be parallel to the axis of the spiral.

The concave outer interior wall of passageway 4 is provided with an abrasive coating 24. This coating may advantageously be applied to the inner surface of a thin, flexible metal strip 26 which may be easily inserted into passageway 4 when cover plate 18 is removed, or threaded longitudinally into said passageway, and which will then be held against the outer wall of said passageway by its own resiliency. This permits the abrasive to be replaced easily, when it becomes worn. The abrasive material used must be-such as is permissable in connection with foodstufis, such as aluminum oxide. Carboundum is objectionable as a possible food contaminant. The abrasive is granular, of perhaps 160 mesh fineness, although this is exemplary only.

The portion of housing 2 forming the tangential inlet 6 of passageway 4 is connected by conduit 28 to the delivery side of an air blower 30, whereby air is caused to travel throughthe passageway to tube 10. With a housing 2 having an outside diameter of about six feet air velocities generally within the range of about 5,000 8,000 feet per minute have been found satisfactory with most grains, but these figures also are exemplary only, and may be changed as may be necessary, or desirable. Grain is fed from a hopper 32 or other source of supply into conduit 28 downstream from blower 30 through a rotary air-lock valve 34 of any suitable type, which prevents air from escaping to the hopper. A grain moistener 36 of any suitable type may be interposed between hopper 32 and airlock 34, it having been found that grain containing a higher degree of moisture than is normal in storage is de-hulled more efficiently than dryer grain. About a 20 percent moisture content has been found to produce good results, although this figure is by way of example only. The grain, thus deposited into conduit 28, is then moved through said conduit to housing 2, and thence through passageway 4 of said housing, by the current of air from blower 30.

The operation of the de-huller, particularly that thereof shown in FIGS. I and 2, is as follows: The kernels of grain, as they enter passageway 4 from conduit 28 and are carried therethrough by the air current, are forced to follow the curved form of said passageway, and are thus forced outwardly by the resulting centrifugal force against abrasive surface 24, moving along said surface with a rolling and sliding action, whereby said abrasive gradually removes the hull from each kernel. The length of said passageway, together with other factors, should be such that the hull is completely abraded away, but none or very little of the interior portions of the kernels, by the time said kernels have transversed the full length of the passageway and enter tube 10 through opening. ll2. The separated hull material is also carried along the passageway by the air flow and enters tube 10. Within said tube, there is provided an upward air flow, as indicated, by arrow 38 in FIG. 2, of such velocity that the lighter hull material rises upwardly through said tubefor disposal, while the heavier de-hulled kernels fall downwardly through the tube for collection and further processing. The upward air flow in tube may be supplied by any suitable means, not shown.

It is of course desirable that the kernels of grain slide, roll, or otherwise move along abrasive surface'24 as smoothly as possible, with as little bouncing, bounding, or separation from said surface as possible, since otherwise the kernels in bouncing away from the abrasive surface and being thrown back thereagainst by centrifugal force would tend to be fractured and broken by the impact, in much the same manner as a snowball rolling and bouncing down a steep, rough hillside. If the grain kernels are naturally somewhat spherical, such as milo or soybeans, they will bounce to a much lesser degree, and are hence less likely to fracture and break. Furthermore, as they move along the abrasive surface, they tend to become still more nearly spherical as the hulls are abraded away, so that they move along the surface still more smoothly and with still less bouncing. Thus if the kernels are originally somewhat spherical, and further are not particularly brittle or fragile, they can withstand a gradually increasing pressure against the abrasive surface. In FIGS. 1 and 2, this gradually increasing pressure is provided by the spiral form of passageway 4, the gradually decreasing radius-of curvature thereof increasing the angular acceleration of the grain as it passes therethrough, and therefore increasing the pressure of the grain against surface 24. The principal advantage of this gradual increase of pressure is that it permits the de-hulling operation to be carried out more quickly, in a shorter passageway 4, than would otherwise be possible. It will therefore be apparent that the species of the invention shown in FIGS. 1 and 2 is best adapted for use with grain the kernels of which are generally spherical, and are not inherently fragile or brittle to any great degree.

However, if the grain has kernels which are not at all spherical, but elongated, so that they would have a strong tendency to bounce along surface 24, at all stages of the de-hulling operation, or if said kernels are particularly fragile or brittle, the action of the FIG. 1 device may be too severe, resulting in a high rate of breakage of the kernels, requiring a gentler action for these grains. Generally, this gentler action may be obtained either by increasing the diameter of the housing to reduce the rate of curvature of passageway 4, or by reducing the speed of grain travel as represented by the air velocity delivered by blower 30. The diameter of housing 2 may of course be increased to reduce the abrasive pressure, but a longer passageway 4 would then be required to complete the de-hulling, and the housing might then exceed practical size limitations. The air velocity of blower 30 can of course also be reduced, but a certain minimum velocity is always required to prevent possible localized filling and clogging of the passageway with grain. FIGS. 3 and 4 show modifications of structure which effectively gentle the abrasive action in such ways as to avoid these difiiculties.

The modification illustrated in FIG. 3 is generally similar to the structure of FIGS. 1 and 2, corresponding parts having corresponding primed numerals where possible, except that housing 2 constitutes a single length of tubing 40 of rectangular cross-sectional contour, and except that passageway 4, instead of having a flat spiral form as in FIG. I, has the form of an inverted pyramidal spiral. That is, each successive convolution thereof is not only of smaller diameter, but is also disposed at a vertically lower elevation than the next preceding convolution, as shown. The advantage of this modification is that it permits the reduction of air velocity therein, thereby providing a gentler action, with no danger that the passageway will become clogged, since the grain is assisted through the passageway by gravity, following a downward path, as well as by the air stream itself. Nevertheless, it still has the advantage, due to its spiral component, of providing a gradually increasing abrasive pressure. This modification is adapted to process grains having perhaps an intermediate degree of sphericity, and an intermediate degree of fragility, as compared to those best processed by the species of FIGS. 1 and 2.

FIG. 4 shows a modification of the device best adapted for processing grains the kernels of which'are still less spherical, and more fragile. This modification is also generally similar to that shown in FIGS. 1 and 2, corresponding parts bearing corresponding doublerimed numerals where possible, except that housing 2" is ormed of a single length of tubing 42 of rectangular cross-sectional contour, and except that passageway 4", instead of having the form of a flat spiral as in FIG. 1, or a pyradmidal spiral as in FIG. 3, has the form of a helix of uniform diameter throughout. This modification has the gravity-assisted action of FIG. 3, permitting reduction of air velocity and due to the substantially constant radius of curvature of passageway 4", provides a substantially constant pressure of the grain against surface 24", rather than the gradually increasing pressures of the other species. This permits effective de-hulling of still less spheral, more fragile grains than is practical with the other species.

While I have shown and described certain specific embodiments of my invention, it will be readily apparent that many minor changes of structure and operation could be made without departing from the spirit of the invention. For example, grain could be propelled through the passageway by its own kinetic energy if dropped from a sufficient elevation to provide the necessary momentum. The apparatus could also be used for removing hulls or the like from materials other than grain, such as nuts, or for cleaning or removing surface layers from mineral particles or the like.

What I claim as new and desire to protect by Letters Patent 1. An apparatus for de-hulling grain or other similar operation comprising:

a. a housing defining an elongated curved passage-way therein, said passageway being curved continuously in the same direction, the radius of curvature thereof being gradually reduced throughout its length,

b. an abrasive coating on the housing surface defining the internal concave wall of said passageway, and

c. means operable to propel grain or the like through said passageway from the end thereof having the larger radius of curvature, whereby said grain is urged against said abrasive coating by centrifugal force.

2. An apparatus as recited in claim 1 wherein said housing passageway has the form of a flat, horizontal spiral, grain being introduced into the outer end thereof.

3. An apparatus as recited in claim I wherein said housing passageway is spirally curved in a horizontal plane, grain being introduced into the outer end thereof, and is gradually lowered in elevation from its entry end to its exit end. 

1. An apparatus for de-hulling grain or other similar operation comprising: a. a housing defining an elongated curved passage-way therein, said passageway being curved continuously in the same direction, the radius of curvature thereof being gradually reduced throughout its length, b. an abrasive coating on the housing surface defining the internal concave wall of said passageway, and c. means operable to propel grain or the like through said passageway from the end thereof having the larger radius of curvature, whereby said grain is urged against said abrasive coating by centrifugAl force.
 2. An apparatus as recited in claim 1 wherein said housing passageway has the form of a flat, horizontal spiral, grain being introduced into the outer end thereof.
 3. An apparatus as recited in claim 1 wherein said housing passageway is spirally curved in a horizontal plane, grain being introduced into the outer end thereof, and is gradually lowered in elevation from its entry end to its exit end. 